Effect of Pressure on Hopping Conduction in Amorphous Ge Alloys

抄録

The electrical conductivity σ has been measured at pressures P to 8 GPa and temperatures T of 77-300K in evaporated amorphous Ge (a-Ge), a-Ge-Cu alloys and a-Ge-Al alloys. The T dependence of σ is well described by a power law at low temperatures below 150 K, which is expected from a multi-phonon tunneling transition process model with weak electron-lattice coupling, rather than the Mott's variable range hopping conduction model. The exponent n in the power law changes with increasing pressure. For both a-Ge_1-xCu_x and a-Ge_1-xAl_x alloys, d (ln n) /dP show positive values in the low pressure region and negative values in the high pressure region. Results are discussed from several hopping conduction models.